The semiconductor chips are typically provided on a foil held in a frame, which is also known as a tape in the field, for the purpose of processing on a semiconductor mounting device. The semiconductor chips adhere to the foil. The frame with the foil is received by a displaceable wafer table. The wafer table is displaced in cycles in order to provide one semiconductor chip after the other at a location and the semiconductor chip which is then provided is received by a chip gripper and placed on a substrate. The removal of the provided semiconductor chip from the foil is supported by a die ejector which is arranged beneath the foil.
In many cases, one or several needles arranged in the die ejector will support the detachment of the semiconductor chip from the foil. Needle-supported methods are known from a large number of patents, e.g. from US 20040105750 or U.S. Pat. No. 7,265,035. In US 2008086874, the die ejector comprises a block with a plurality of rods which have a flat end and a second block with a plurality of needles, with the needles being arranged between the rods and the surface of the flat end of each rod having a multiple of the cross section of a needle. For the purpose of detaching the semiconductor chip, the block with the rods is lifted at first and the block with the needles is lifted until the needles protrude beyond the rods.
A die ejector with supporting structures is known from WO 2005117072, on which the foil rests during the entire detachment process. The supporting structures are enclosed by rods with a flat end which are displaceable in the direction towards the semiconductor chip as well as in the opposite direction. The supporting structures and the rods can also be formed by a plurality of individual tappet rods which are arranged in the manner of a matrix.
A die ejector is known from US 20050059205 which comprises several plates which are disposed adjacent to one another, and for the purpose of detaching the semiconductor chips are lifted either jointly and then lowered sequentially from the outside to the inside or are lifted from the outside to the inside sequentially in order to form a pyramidal elevation that protrudes beyond the supporting plane.
Various methods are also known in which the semiconductor chip is detached from the foil without the use of a needle. In U.S. Pat. No. 4,921,564, the foil beneath the semiconductor chip is subjected to a vacuum at many individual locations in order to remove the foil at these places from the semiconductor chip. In US 2002129899 and U.S. Pat. No. 7,238,593, the foil is drawn over the edge of the die ejector and removed thereby. In U.S. Pat. No. 6,561,743, the foil is drawn off in a boundary region of the semiconductor chip by means of vacuum and then displaced relative to the semiconductor chip which is gripped by the chip gripper, with the semiconductor chip being detached from the foil.
The thickness of the semiconductor chips to be detached decreases continually. Currently, the thickness is in many cases less than 100 micrometers, with a tendency towards further reduced thicknesses of 20 to 10 or even 5 micrometers. An additional factor is that the wafers are sometimes provided with an adhesive layer on their reverse side. The adherence of the semiconductor chips on the foil will thus increase. The technologies as described above are often no longer sufficient and/or are not reliable enough or are relative slow, which means that it often happens that a semiconductor chip is damaged or destroyed during detachment.